Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1998-12-30
2002-10-08
Kizou, Hassan (Department: 2662)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S232000, C370S233000
Reexamination Certificate
active
06463035
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to traffic control signaling in a fast packet network carrying Internet protocol packets and, more particularly, to the initiation of control signaling upward between layers one and two of a fast packet protocol such as the frame relay protocol and layers three, four or five of an Internet protocol such as the TCP/IP protocol, for example, for data flow control upon receipt of a congestion message or for other purposes.
2. Description of the Related Arts
Referring to
FIG. 1
, there is shown an overview of a known fast packet network for example, a frame relay or cell relay network, that is carrying packetized traffic between customer locations. By frame is intended a larger data carrying capacity within a single entity than a cell. A cell may comprise one or more data packets, typically, a predetermined number of packets, and a frame is of variable length. The stacks
101
and
102
at the left and right respectively indicate stacks from the known open systems interconnect (OSI) model for describing layers of potential data transmission. Typically, customer applications software
103
runs on, for example, a personal computer workstation, labeled customer computer at location A or CCA and customer applications software
104
runs on the customer computer at location B or CCB. These talk to each other over the fast packet network at various levels of communication. The customer computer may be any intelligent communications terminal device having a controller and memory.
At level 1, there exists, for example, communication over a local area network (LAN) cable between the computer workstation CCA, CCB and the router
105
,
106
, for example, an ACT Networks SDN-9300 or other router known in the art. The router
105
,
106
is connected via the customer's CSU/DSU interface card
106
,
107
to a time division multiplex (TDM) link to a comparable network's CSU/DSU interface card
108
,
109
. Typically, the area represents the facilities of an interexchange carrier
112
such as AT&T and are shown in greatly simplified form. At the edge of the IEC network may be a frame relay router
110
,
111
which may, for example, comprises an ACT Networks SDM-9400 or SDM-9500 or other router known in the art. In between these edge switches, not shown, may be a satellite uplink, not shown and other intermediate switches.
At layer
3
, is the Internet Protocol (IP) layer. The workstation CCA or CCB communicates with the respective router
105
,
106
. There is no Internet protocol or TCP protocol communication within the fast packet portion of the network
112
. At layers
4
and
5
, the TCP protocol operates and at layers six and seven, the http.ftp.telnet high level protocol operates. These layers are strictly between work stations CCA and CCB.
Consequently, starting at the 7 layer customer computer CCA or CCB, each stack of protocols can be understood as executing software process on the individual network element depicted. For example, the complete 7-layer stack executing on the customer computer may, in actuality, be, for example, an inetd daemon applications package
103
operating under the UNIX operating system or a comparable package operating under a Microsoft Windows operating system or other system known in the art to provide protocol-based end-to-end communications services. The flow of data in the network is from applications software
103
all the way across the network to applications software
104
.
The exchange of protocol-based control information in such a network is peer to peer. For example, if the TCP protocol processes on work station CCA exert flow control on the data stream, then it is exchanging flow control information with its peer TCP process on work station CCB. The same thing is true for IP and http and so on.
The IXC fast packet, for example, frame or cell relay transport is shown in the shaded area of FIG.
1
. As already indicated, there could be many switches, or as few as two, switches, namely the depicted edge switches. Transport of fast packet data is at layer
2
; the frame relay protocol is between routers and may be I.E.E.E standard 802.3 logical link control (LLC) from the customer router
105
,
106
to the work station CCA or CCB. Layer
2
is where control such as data flow control is exerted in a fast packet network, not at a higher layer such as layer
4
as in TCP.
Now referring to
FIG. 2
, similar reference characters are used to denote similar elements. There is shown a similar figure emphasizing one end, for example, the CCA end of the network of FIG.
1
and with arrows shown designating what happens in the event of traffic congestion in the fast packet network. The X signifies the sensing of congestion at a frame relay switch
201
within a fast packet network
112
such as the AT&T frame relay network. A key at the top of the drawing indicates the typical interface between the IXC and the customer premises equipment, although, in other embodiments, router
105
may comprise a portion of network
112
.
Starting at the 7-layer customer computer CCA, outbound traffic traverses the customer router
105
and then may encounter congestion at the second network switch
201
. When congestion is sensed in a fast packet network, it is known to originate congestion messages at level
2
in a forward and backwards network direction. The forward congestion message FECN proceeds to the right (forward) and the backwards congestion message proceeds to the left (backward) by setting a bit within the cells or packets known as the FECN and BECN respectively to 1. For example, when congestion is noted, the forward message has FECN equal to 1 and BECN equal to 0. The backward message has FECN equal to 0 but the BECN equal to 1. Following the path of the BECN message, the message is passed by the edge switch
110
to the router
105
. The edge switch
110
according to the prior art is typically not programmed at all to react to the BECN message. Presently, the router
105
strips or discards the BECN message. The router
105
is, like the edge switch
110
, not presently programmed to react at all to the receipt of a congestion message. The fast packet protocols, including the frame relay protocol, are silent on what the end router is to do with the congestion message or any action to take. Congestion continues and dropped frames, cells and packets occur until the TCP layer finally senses longer acknowledgment times and/or missing packets. The TCP layer, being the first layer that is end-to-end or peer to peer, is the first to react but is a layer that controls the presentation of data to the user at their work station and from the executing computer process
103
to the network. A layer
4
process may be executing on the router
105
, but such a process is also typically passive to congestion at layer
2
. Enhanced layer
4
control functions are known, for example, firewall (security) functions, but these are not data flow control functions. In the typical case, the layer
4
router process is passive and so is not shown. In summary, it is believed that according to prior art processes, there is no slowing of data presentation to the network at workstation CCA even though network congestion is sensed at a frame relay switch
201
of the network and, eventually, frames (cells) are dropped due to the congestion.
Recently, the United States federal government has enacted legislation to encourage the delivery of Internet services to remote school districts, for example, that may only be reached by satellite. Examples of such school districts may comprise outlying Indian villages in rural Alaska, whose only telecommunications service is via satellite. Satellite introduces absolute delay into any data path due to the length of time it takes to travel to and from a geosynchronous satellite. Flow control becomes more acute because of this delay which would be experienced in a prior art flow control scheme where reliance on layer
4
TCP flow control measures is the only alternativ
AT&T Corp
Spafford Tim
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